1. Field of the Invention
The present invention relates to a technique for positioning an optical element and fixing the same.
2. Description of the Background Art
In an optical element module (i.e., a module comprising an optical element(s), such as a module comprising an optical fiber and an optical communication device), conventionally, in order to position a microscopic optical element with respect to a predetermined optical axis and fix the optical element (in other words, for alignment, to adjust the position and orientation of the microscopic optical element), the optical element is moved in one or two directions and positioned, being in contact with a contact surface(s) of a holding member, and then fixed by filling its surrounding with solder or a bonding agent (e.g., a bonding agent containing UV curing resin), or by laser fusion bonding with emission of high-energy pulsed light such as YAG laser or glass fusion bonding with glass powder.
For example, since a semiconductor laser used in a light source or the like has a large divergence angle of an emitted light beam (e.g., several tens degrees), in general, the light beam is changed into a parallel ray by using combination of collimator lenses. Specifically, as shown in FIG. 1, a holding member 92 to which a semiconductor laser 91 is fixed is provided with a contact surface 92a and an adjustment assisting member 94 on which a collimator lens 93 is fixed is inserted in the holding member 92, being in contact with the contact surface 92a. Then, the adjustment assisting member 94 is moved in a direction indicated by the arrow 95 of FIG. 1 to perform a collimating adjustment for adjusting the degree of parallelization of the light beam, and the adjustment assisting member 94 and the holding member 92 are fixed to each other.
In a multichannel optical fiber connector which is used in applications using optical fibers, such as optical fiber communications, (which is used, for example, in multichannel transmission to increase transmission capacity) and a light source unit such as a laser scan type image output apparatus and the like, a plurality of optical fibers are one-dimensionally or two-dimensionally arranged with high accuracy. In order to arrange the optical fibers, grooves 96 each having a V-shaped section are formed in such an arrangement as shown in FIG. 2 with a diamond cutter or the like in a holding member 97 formed of ceramics. Each optical fiber 98 is positioned, being in contact with side surfaces 96a of the groove 96, and then fixed.
FIG. 3 shows positioning and fixing of a bare chip 191 of semiconductor laser (hereinafter, referred to as a “semiconductor laser”) and an optical fiber 192. Also in this case, the optical fiber 192 is positioned relatively to a holding member 193 on which a groove 193a having a V-shaped section is formed, by bringing a tip portion of the optical fiber 192 into contact with side surfaces of the groove 193a. The semiconductor laser 191 supported by a collet (not shown) is positioned with respect to the optical fiber 192, being in contact with an upper surface of the holding member 193, and fixed by a bonding agent (such as solder).
In a case of coupling (or splice) as shown in FIG. 4 where an optical waveguide element 194 and a plurality of optical fibers 192 are positioned and fixed to each other, the optical waveguide element 194 is positioned relatively to the holding member 195 and fixed thereto. On a positioning member 196 on which a plurality of grooves 196a each having a V-shaped section are formed and a positioning member 197 on which a groove 197a also having the V-shaped section, a plurality of optical fibers 192 are fixed with a bonding agent or the like, being in contact with respective side surfaces of the grooves 196a and 197a, and the positioning members 196 and 197 are fixed onto the holding member 195, to position the optical fibers 192 with respect to the optical waveguide element 194.
There is relevant technique which is shown in the following document.
“Optical and Electro-optical Engineering Contact” (Japan Optomechatronics Association, Dec. 20, 1996, Vol. 34, No. 12 (1996), p.p. 619–627 and 636–640).
“OPTRONICS” (Optronics Co., Ltd., Apr. 10, 1999, No. 4 (1999), p.p. 129–133 and 140–149).
“OPTRONICS” (Optronics Co., Ltd., Jul. 10, 1999, No. 7 (1999), p.p. 149–155).
In the exemplary case of FIG. 1, since the collimator lens 93 can be moved only in the direction indicated by the arrow 95 and the position and orientation thereof with respect to other directions depend on processing accuracy or the like of the members, it is difficult to perform an adjustment even in a case where a fine adjustment is needed, such as where an emission angle of the light beam from the semiconductor laser 91 slightly deviates. If it is intended to increase the degree of freedom in adjustment, the structure becomes complicated and this causes a problem of increasing a manufacturing cost and the like.
In the exemplary case of FIG. 2, though ceramics which is less affected by temperature change or the like is generally used as the holding member 97, the ceramics is a costly material and needs a high machining cost. Further, with this method, it is difficult to deal a complicated arrangement.
In the optical element module of FIG. 3, though the optical fiber 192 can be adjusted to a predetermined position only in the Z direction, the position and orientation with respect to other directions depend on the shape of the groove 193a. Though the semiconductor laser 191 can be positioned with respect to the optical fiber 192 by moving it in the X and Z directions, the position thereof in the Y direction can not be determined freely. As a result, while it is possible to ensure high relative positioning accuracy of 1 to 2 μm in the X and Z directions, the relative positioning accuracy in the Y direction becomes worse (e.g., several μm) than that in the X and Z directions since it depends on the machining accuracy of the groove 193a and the reproducibility in thickness of the bonding agent.
In the optical element module of FIG. 4, while it is possible to ensure the positioning accuracy of about 0.2 μm with respect to the optical waveguide element 194 in the X and Z directions by applying a bonding agent or the like between the positioning members 196 and 197 and the holding member 195 and adjusting the bonding position, the positioning accuracy in the Y direction is about 1 μm due to variations in machining accuracy of the grooves 196a and 197a and diameter of the optical fibers 192, and the like.